1. Field of the Invention
The present invention relates to a semiconductor package, and particularly, to a technique of preventing the generation of leak current due to photoexcitation in a thin semiconductor package.
2. Description of the Related Art
An earlier semiconductor package is thinned by (1) thinning an interposer of the package and by (2) thinning a resin mold of the package. An example of a semiconductor package thinned by the techniques (1) and (2) is a Thin Quad Outline Nonleaded (TQON) package. The TQON package employs a flip-chip connection process and guarantees a package thickness of 0.5 mm or thinner.
FIG. 1 is a sectional view showing a semiconductor package according to a related art, and FIG. 2 is a plan view showing a wiring layer formed on an interposer of the package of FIG. 1.
In FIG. 1, the wiring layer 48 is formed on the interposer 40. A semiconductor chip 10 is mounted upside down and connected to the wiring layer 48 by flip-chip contacts 20. The interposer 40, the wiring layer 48, and the contacts 20 are sealed with an underfill material 30. The chip 10 and the underfill material 30 are sealed with a resin mold 60.
Under the chip 10, there are only the contacts 20 and there is no wiring layer 48.
In FIG. 2, the wiring layer 48 includes conductors that are spaced widely apart from one another.
The thin package according to the related art has a problem (1) that the interposer allows the transmission of light which optically excites semiconductor elements in the semiconductor chip and generates leakage current causing malfunctions. This is because, in order to thin the interposer, the related art fabricates the interposer from a resin substrate made of, for example, glass epoxy resin, Bismaleimide Triazine (BT) resin, or polyimide (PI) resin, instead of a metal lead frame. The related art also has a problem (2) that the resin mold on the semiconductor chip allows the transmission of light, in particular, light of 780 nm or longer in wavelength which optically excites the semiconductor elements and generates leakage current causing malfunctions. The problem (2 ) occurs when the resin mold on the semiconductor chip is excessively thinned to reduce the thickness of the package.